The enclosed pencil sketches will give you an idea of the results
obtained from sectioning four lots of material from the two samples
of catkins that you sent, two lots from each sample. Since the
sample collected May 25 at the time of catkin fall was old enough
to contain mature pollen and showed only anthers of the two types
described herewith I think we may safely conclude that the tree is
male sterile because of the failure of the mother cells to
function. It is odd that in some anthers the pollen-mother-cells
develop (type 2) while in others they do not (type 1). For this we
have no explanation; nor can we explain why the tree is male
sterile. I am afraid these phenomena will remain a matter of
conjecture for some time to come. Since sterilities of this and
other sorts in most other plants are largely genetic, that is,
controlled by one or more genes that are inherited in Mendelian
fashion, it is likely that such is the case here. You and I will
not live long enough, however, to grow the necessary number of
generations of trees to clear up these matters.

"In the course of routine preparation of other material I plan to
run up other lots from your samples, and I will let you know if
anything different turns up. I believe we may safely conclude,
however, that the results reported herewith are representative."

In further explanation, Dr. McKay submitted the drawings shown on page
57, and says:

"Four lots of material were sectioned, two from the collection of
May 6 and two from that of May 25. Of these, two gave anthers of
type one, and two of type two. More material will have to be